Abstract

The shear strength of masonry is the function of many factors, but current research indicates
that bond quality is the primary factor. The bond strength is a key parameter representing
structural integrity and water-tightness of the masonry system. However, masonry is
characterized by low bond strength, and is quite a complex material to analyse due to its
inherent variations. The quality of the bond is reliant on, the weather, the quality of the
workmanship and the quality of materials used.
Therefore, this study investigated ways of improving the bond performance of mortar joints by
the use of admixtures as well as examining the efficacy of Acoustic Emission (AE) techniques
in monitoring fracture mechanisms. Laboratory based Acoustic Emission (AE) monitory
techniques were used on masonry triplets under static and repeated shear loading, in order to
investigate the shear bond strength characteristics, and to identify a mortar that will exhibit the
long-term properties needed for a masonry structure to be subjected to cyclic loading, such as
masonry arch bridges. The FE micro-modelling method was used to predict the shear
behaviour of the triplet. Moreover, Photo-elastic analyses were used to investigate the stress
distributions within the triplets under shear stress, in order to check the output from FE
analyses.
The investigation showed that the addition of SBR to mortar improves its performance under
both static and cyclic loading when compared to the control sample, all in contrast to the
addition of Latex 114 admixture which had the opposite effect. Additionally, the AE technique
was found to be useful tool in providing valuable data about the full fracture behaviour during
static and cyclic loading. The FE analyses proved to be capable of predicting shear strength to
a reasonable degree of accuracy. The Photo-elastic technique was found to be a reliable and
simple method of checking the stress profile output from the FE analyses.